I. Field of the Invention
This invention relates generally to medical apparatus, and more particularly to an implantable, magnetically-actuable valve mechanism which, when positioned in the urethra of a male or female patient, acts to selectively block urine flow, thus providing a treatment for urinary incontinence.
II. Discussion of the Prior Art
Urinary incontinence in both males and females remains a persistent problem, even though various methods and devices have been devised and proposed to treat the problem. The use of a catheter and associated collection bag with a clamping device on the catheter is useful only for relatively short-term situations. The presence of a long-term, indwelling catheter often leads to bladder infections in that the catheter provides a rather direct passage for bacteria or other microscopic organisms into the bladder. The use of special waterproof, water-retaining pants remains an option, but many who suffer urinary incontinence shy away from their use due to embarrassment and potential odor problems.
Another approach in treating urinary incontinence has involved the implantation of a valve into the urethra where the valve has a means operable external to the body to actuate it from a closed, urine-blocking position to an open, urine-draining position. In this regard, reference is made to the Isaacson U.S. Pat. No. 3,812,841 and the Beyar et al. U.S. Pat. No. 5,004,454. In each of these arrangements, the valve comprises a tubular body which may be inserted by an appropriate insertion stylet into the urethra. Contained within the valve body is a magnetically actuable valve member. When a permanent magnet is brought into proximity with the implanted valve, but exterior to the body, the valve may be shifted from its closed to its open position to allow the bladder to empty through the valve. Removal of the external magnet restores the valve to its urine-blocking disposition.
Each of the prior art magnetically-actuable, urinary incontinence valves described in the Isaacson '841 patent and the Beyar et al. '454 patent has design defects which render them unsuitable for their intended purpose. In particular, in each of the designs, a coil spring used to urge the valve against its valve seat is a tension-type spring which is continuously exposed to the bladder and, therefore, continuously bathed in urine. This can lead to valve failure when pitting of the metal of the spring occurs and when salt deposits build up on the spring element. Moreover, in the event of spring failure, it is possible for parts of the assembly to snap loose and be projected with force into the bladder. The device of the Beyar et al. patent also is deficient in that the valve orifice through which urine flows when the valve is actuated is quite small and the displacement of the valve surface from the valve seat is so small that urine flow is reduced to a trickle at best. The valve displacement from its seat is restricted by the fact that the cone-shaped valve member 21 can only be displaced very slightly by the external magnet because its movement is constrained by the walls defining the bore 12 of the valve body.
In each of these prior art designs, a stylet with a threaded distal end is used to engage the valve body either prior to insertion or at the time of removal. It is difficult, especially at the time of removal, to engage the threaded end of the stylet within the proximal end of the valve body when the valve body is in the urethra.